A switching means between a normal stitching and a thread winding depends upon two operations.
In a conventional sewing machine, the thread winding mechanism is engaged with a power source of the sewing machine, and a clutch mechanism is operated so that a mechanism related with rotation of an upper shaft is separated from the power source. If an operation of a clutch mechanism were forgot and the thread were wound, a needle bar would be actuated together with the thread winding. Such an accident is not desirable for the safety of operation.